A distribution is approximately Normal when the Normal distribution can be used as an approximate distribution. This is common when the number of samples or parts making up a distribution grows; for example, if you have 100 coin tosses the resulting Binomial distribution is, for most purposes, approximately Normal. This is often helpful as many statistical tests rely on the data being Normal distribution. The Central Limit Theorem explains why it is so common to see approximately Normal distributions.
Used on pages 47, 48